The present invention is related to a driving assistance apparatus operated in such a manner that while images of plural cameras are synthesized with each other so as to achieve a driving assistance purpose, for example, a parking assistance at a parking lot, a condition of an area around a vehicle, containing a dead zone of a vehicle driver, may be easily displayed/guided. More specifically, the present invention is directed to such a driving assistance apparatus capable of displaying such an area by way of safety and easy-understandable display manners in such a manner that while a distance measuring sensor, e.g., an ultrasonic sensor is employed in addition to these cameras, information of this distance measurement is effectively superposed on the synthesized image.
Referring now to drawings, a description will be made of a conventional driving assistance apparatus with respect to background art in this technical field.
FIG. 10 is a schematic block diagram for representing an arrangement of a conventional driving assistance apparatus. In FIG. 10, the conventional driving assistance apparatus is arrange by a plurality of cameras 1, a plurality of virtual observing point converting unit 2, and an image synthesizing unit 3 for synthesizing image information with each other, which is supplied from this virtual observing point converting unit.
While cameras 1 are mounted on a vehicle, these cameras 1 may pickup, as a moving picture, images regarding a condition of an area around the own vehicle along a certain direction, for example, a forward direction, a backward direction, or a side direction. It should be noted that a total set of camera 1 is not limited to one set, but may be selected to be plural sets. Normally, if images of a peripheral area of a vehicle is wanted to be picked up without any dead zone, then four sets to approximately ten sets of cameras 1 may be mounted on this vehicle.
Normally, an image picked up by the camera 1 corresponds to such an image which can be observed in the case that an observing point is positioned at an image pick-up element of the camera 1. Generally speaking, while an acquired image is subdivided into subdivision images, each of these subdivision images is enlarged, compressed, deformed, and rotated, so that this acquired image may be converted into such an image (moving picture) at an arbitrary observing point as well as an arbitrary observing line from the observing point of the above-explained image pick-up element. For instance, assuming now that the camera 1 is installed in such a manner that an image of a road is picked up from an upper oblique direction in the vicinity of a side mirror of a vehicle, if the observing point of the camera 1 is converted, then the present road image may be converted into such an image which is obtained in such a manner that while the observing point is set to a front edge portion of the vehicle, the observing line is positioned in parallel to the road. Alternatively, the present road image maybe converted into such an image which is obtained in such a manner that while the observing point is positioned at upright of the vehicle, this observing point is directed downwardly.
The virtual observing point converting unit 2 performs the previously-explained virtual observing point converting operations based upon the mounting positions and the mounting attitudes of the respective cameras 1 at predetermined observing points and also at predetermined observing lines (alternatively, predetermined observing points and observing lines may be substituted by such a manner that these observing points/observing lines are later designated by a vehicle driver).
For a better understanding of the technical contents of the conventional driving assistance apparatus, the below-mentioned description is made based upon the following conditions. That is, while an observing point is positioned above a head of the own vehicle, for example, above 10 meters at upright of the own vehicle, a virtual observing point conversion is carried out based upon such an observing line that a vehicle driver observes from this upright position just under the own position.
The image synthesizing unit 3 synthesizes observing-point-converted images with each other, which are acquired from the same observing point by operating the virtual observing point converting unit 2. Assuming now that a plurality of cameras 1 are mounted at a peripheral portion of the vehicle without any dead zone, observing-point-converted images may be synthesized to obtain such an image as if all of the peripheral areas of the own vehicle were observed from the upright position.
For instance, such a condition as shown in FIG. 11A is assumed, namely, such a case that the driver of the own vehicle tries to perform parallel parking is predicted. FIG. 11A corresponds to an image which is actually observed from the upright direction of the own vehicle. Also, FIG. 11B corresponds to an image diagram of a synthesized image which maybe obtained from the condition of FIG. 11A by the conventional driving assistance apparatus.
In this case, since the cameras 1 are mounted on the own vehicle, all portions of the own vehicle cannot be completely observed in view of the theoretical point. In other words, it should be understood that the portion of the own vehicle shown in FIG. 11B corresponds to such a model, but is not equal to the actual image. This model is predicted from a previously-measured dimension of the vehicle, and a shape of this vehicle.
Also, a white lane line drawn on a road surface and a relatively low object are displayed on the synthesized image such as an actually viewed image from the upright position as shown in FIG. 11B, and this synthesized image may constitute a very friendly image for a vehicle driver. However, for example, since the observing points of the adjoining vehicles (three-dimensional objects) are forcibly converted into such images, these image of the adjoining vehicles may be sometimes deformed as actually-not-available images. These converted images are produced in such a manner that images picked up along the transverse direction are forcibly converted into images observed from the upright position.
In FIG. 11B, although the images of other vehicles should be originally observed as the images of FIG. 11A, these vehicle images are observed as follows: These vehicles are pushed by their sides and are largely deformed.
As previously described, while the conventional driving assistance apparatus employs a plurality of cameras which are mounted on the limited places of the vehicle, these images are processed by way of the observing-point conversion and the image synthesizing operation, this conventional driving assistance apparatus may provide to the vehicle driver, such images which could not be so far obtained form the specific observing points, for instance, the image picked up from the upright position of the own vehicle. Thus, the vehicle driver can understand the condition around the own vehicle at a glance.
However, the above-explained conventional driving assistance apparatus owns the following problem. That is, as previously described in the foregoing description of the background art, as to the synthesized image which is provided by the conventional driving assistance apparatus, since the observing points of the adjoining vehicles (obstacles) are forcibly converted into such images, these images of the adjoining vehicles may be sometimes deformed as actually-not-available images. These converted images are produced in such a manner that images picked up along the transverse direction are forcibly converted into images observed from the upright position. As a result, it is practically difficult to grasp the positional relationship between the own vehicle and other vehicles.
For example, in such a case that a vehicle driver only observes this synthesized image when the vehicle driver parks the own vehicle, there are such risks that this vehicle driver mistakenly grasps either a distance or an interval between the own vehicle and other vehicles, so that the own vehicle is made in contact with other vehicles. For instance, as indicated in FIG. 11A, although the own vehicle is approached to another vehicle by the distance “d1” under actual condition, the following phenomenon may occur. That is, as represented in FIG. 11B, the vehicle driver mistakenly observes that the own vehicle is separated from another vehicle by the distance “d2” on the synthesized image.